Meeting Abstract
While most fish use their fins for swimming, some benthic fish use their fins to “bottom-walk” on the seafloor. This particular form of locomotion is believed to allow them to remain cryptic while approaching prey or to avoid predation. The underlying morphologies that enable fish to bottom-walk are not well-described. The Antarctic plunderfish, Histiodraco velifer uses synchronized pelvic fin movements to “walk”, or punt, along the ocean floor. Like other notothenioid fishes, they lack swimbladders yet have less ossified bones which increases buoyancy. However, no other notothenioids are known to bottom-walk. The goal of this study was to compare the pelvic morphologies of three notothenioid fishes, and describe the underlying pelvic girdle morphology that enables bottom-walking in H. velifer. Three specimens each of H. velifer, Trematomus bernacchii, and Gymnodraco acuticeps were microCT imaged and their pelvic structures segmented. We found that these representatives of diverse notothenioid families display similar pelvic morphologies, including reduced ossification of the pelvic plates compared to other, non-notothenioid fishes. Notably, for all notothenioids examined the anterior and posterior portions of the pelvis are cartilaginous, lacking ossification, while ossification is increased where the pelvic fins attach to the pelvic plate. In comparison to the other notothenioids, H. velifer has an elongate pelvis, which may allow for increased muscle attachment surface area to power the bottom-walking behavior. In all species, pelvic fin rays were more ossified than the pelvic structures and displayed an enlarged dorsal process for muscle attachment.
